Exposure of infants during pregnancy to the pesticide bendiocarb reduced important immune system cells and measles antibodies. This would be expected to increase risk of measles infection. The chemical was commonly used in gardens and inside homes but was banned and removed from the U.S. market in 2001. It is still used today in other countries including Africa for malaria prevention. Bediocarb-exposed infants had "lower frequency of naive CD4 cells" which are essential for mounting and organizing an attack against viruses. Bendiocarb also decreased the number of regulatory T cells which are critical for calming down the mother's immune system to prevent rejection and miscarriage of the fetus.
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DISCUSSION
esticides are important tools for malaria control but may have unanticipated effects on human health. We found that bendiocarb, a carbamate pesticide in common use worldwide, is absorbed in pregnant women, transferred to the fetus, and remains detectable in infancy. Exposure to bendiocarb in utero had clear biological effects on the fetal immune system, independent of its impact on malaria vector control. These included dose-dependent alterations in immune cell homeostasis and function, encompassing both lymphoid and myeloid-derived lineages, including decreased FoxP3+ regulatory CD4 cells, increased cord plasma cytokines and chemokines, increased T cell production of inflammatory cytokines, and decreased T cell proliferation. Together, these changes suggest a shift in fetal T cell homeostasis toward an inflammatory response, and away from regulatory differentiation that is believed to be critical for the maintenance of maternofetal tolerance19,20.
ABSTRACT
The use of pesticides to reduce mosquito vector populations is a cornerstone of global malaria control efforts, but the biological impact of most pesticides on human populations, including pregnant women and infants, is not known. Some pesticides, including carbamates, have been shown to perturb the human immune system. We measure the systemic absorption and immunologic effects of bendiocarb, a commonly used carbamate pesticide, following household spraying in a cohort of pregnant Ugandan women and their infants. We find that bendiocarb is present at high levels in maternal, umbilical cord, and infant plasma of individuals exposed during pregnancy, indicating that it is systemically absorbed and trans-placentally transferred to the fetus. Moreover, bendiocarb exposure is associated with numerous changes in fetal immune cell homeostasis and function, including a dose-dependent decrease in regulatory CD4 T cells, increased cytokine production, and inhibition of antigen-driven proliferation. Additionally, prenatal bendiocarb exposure is associated with higher post-vaccination measles titers at one year of age, suggesting that its impact on functional immunity may persist for many months after birth. These data indicate that in utero bendiocarb exposure has multiple previously unrecognized biological effects on the fetal immune system.